A lover and his lady

There are ways of seeing and you see what you look for, apparently.

In school we learnt Wordsworth's 'Daffodils' and Coleridge's 'Rhyme of the Ancient Mariner'.
Many years were to pass before I re-read the poems, seeing in them a record of  depression. 

Recently, I was thinking of the story of  the 'Lady of the Lake', set in  'Llyn-y-Fan-Fach', in Carmarthenshire.
Dating from the twelfth century, it tells of a young man tending his flock when he sees a beautiful creature emerging from a lake. He falls in love with her and  you can hardly blame him, because he probably met few comely maidens.

Wondering how to entice her, he offers his bread, which she refuses, arrogantly calling,
'Cras dy fara, Nid hawdd fy nala'.
In English  this means: 'Your bread is hard, it is not easy to catch me', an unpromising  beginning.

When his mother hears what has occurred, instead of being surprised that a girl popped out of the lake and spoke to her son, she suggests taking unbaked bread-dough next time, which might be more to the lady's taste.

With hope in his heart and the wet dough in his napkin, he sets out the next morning. Magically, the lady appears and, undeterred by her previous rebuff, he presents his offering.

Again, she scorns his bread, the representation of his love, with the words:
'Llaith dy fara, Ti ny fynna', which means: 'Damp is your bread, I will not have thee'.

Not many men would risk further rejection, but the ardent swain decides to take some half-baked bread the following day.

All day he waits, but there is no sign of the lady. Dusk is falling and, in despair, he turns for home, throwing the bread into the water.

Just then, the lady appears. The hopeful lover explains he has no riches to give her, just himself.  This declaration works the magic and she agrees to marry him.

She has no interest in the worldly goods the bread represents, but just himself and his love. (It would have made things so much easier if she had said so instead of playing games.)

Things were not straightforward, though.  The lady made conditions. If her husband-to-be struck her three times, however lightly, she would disappear back into the lake.  Despite this, the pair marry and have a son.

Preparing to go to a christening, the lady fusses about the child, saying she had to take this and that with her.
(I am tempted to ask here if this is the first sign of  post-natal anxiety, the inability to leave the house without checking endlessly that nothing has been forgotten? Or am I reading this wrongly?)
The husband grows impatient and taps her back.
She tells him he has struck her for the first time. Dramatically, she claims the child would have died if she had not gone through the various rituals. (Is this a part of her hysterical personality?)

A year or so later another baby boy is born.
At a church service, a wedding, the wife cries loudly (a display of her nervous disposition?) and her husband taps her lightly.

This is the second 'knock'. Her tears, she explains, are because she sees disaster for the young couple.
(Obviously, she cannot contain her emotions, and she seeks attention in public places. She does not doubt her predictions, either).

During the third year of marriage, the wife gives birth to another baby. At a funeral, she laughs hysterically and her husband slaps her.
This is the fatal blow. The lady seems unrepentant about laughing, declaring she was glad the dead person had left the misery of this life behind.

Soon after this, she disappears into the lake, taking her cattle with her, leaving her husband and three sons distraught.

As the boys grew, the 'Lady of the Lake' sometimes appeared to her eldest son, Rhiwallon.
She taught him how to heal using herbs and flowers and so powerful were his remedies that he attended Rhys, the Lord of Dynevor and Ystrad Towy. His two brothers also learnt the secrets of healing.

For centuries the descendants of the 'Physicians of Myddfai', as they became known, were active in the area. Rice Williams, who died in 1842, was believed to be a direct descendant of the 'Lady of the Lake' and many travelled to seek his advice.

Did the watercreature suffer from some form of mental disorder, such as  post natal depression or was she one of the fairy folk? How are we supposed to read the story?